PF_ALGNMNT
PF_ALGNMNT(startoff));
PF_ALGNMNT(startoff + sizeof(sack.start)));
PF_ALGNMNT(ts - opts));
tsr, htonl(tsecr), PF_ALGNMNT(tsr - opts));
htons(maxmss), PF_ALGNMNT(mssoffopts));